Castlevania: Lords of Shadow
For the longest time (starting with Symphony of the Night where he served as assistant director), one man was in charge of overseeing the Castlevania series: Koji Igarashi. It was through his stewardship that the series saw it's greatest popularity as it transitioned from action plotformers to Metroidvania adventure games. After years shepherding the series, though, he eventually left to pursue his own projects (whether this was his choice or Konami forced him out, much like Hideo Kojima, creator and director of the Metal Gear series is a point of an discussion).
After his departure it was up to a new team to cary on the series (in a new direction to presumably, help boost sales). That new team was actually a collaboration between MercurySteam and Kojima Productions and the reulting product was Castlevania: Lords of Shadow. Functioning as a reboot for the whole series, Lords of Shadow, Gabriel Belmont, a warrior of the Brotherhood of Light who was sent to battle the titular Lords of Shadow and save the world.
The game marked a radical change in direction for the series. Ditching all the previous continuity from the previous games in the series, little was left in Lords of Shadow that fans would recognize beyond a Belmont carrying a whip (and that whip wasn't even called the "Vampire Killer"). Gone was the Metroidvania emphasis on exploration, instead leading to a much more linear, action-heavy game. Many fans were disappointed, too, in the way the game played, often beyind likened to God of War (although it should be noted that similar criticism were leveled at Lament of Innocence, calling it little more than a Devil May Cry clone, however fair that may have been -- no game is created in a vacuum, so some inspiration will always be ineveitable).
Still despite the rocky reception from long-time fans, Lords of Shadow proved to be a success, spawning two sequels and defining the games series in its (so far) final chapter of life. It remains to be seen if future games will take their inspiration from this reboot of the series or go in some new (or much older) direction if it ever does move forward again.